Just before you rip open your Easter egg box next weekend and gobble up the chocolate, take a moment to have a good sniff of the unwrapped egg. Don't worry if it's the shell of a giant Cadbury's Creme Egg you're smelling rather than Valrhona's finest beans – just hold the chocolate up to your nose and breathe in its scent, because latest research suggests "odour du chocolat" improves your mood.

This happy news comes straight from the Human Olfaction Laboratory at Middlesex University, where Neil Martin, a reader in psychology, investigates the effects of room smells on human behaviour. In his laboratory, Martin has a square box called an AromaCube, which heats up "odorants" contained in tiny glass bottles and then percolates the smell around the room. From that box, he discovered the power of chocolate in an experiment where he filled rooms with three smells, one of chocolate, a "malodour" of machine oil, which most people find unpleasant, and a lemony, pleasant-but-alerting odour, then monitored testers' moods.

"The aim was to compare the effects of pleasant and unpleasant ambient odours on stress, anxiety, depression and mood," Martin explains. "And whilst we're still continuing the experiment, so far it seems that the smell of chocolate really does make people less stressed and anxious, and more relaxed."

Chocoholics will also be pleased to hear about some of Martin's earlier research. "In another study, we looked at the effect of chocolate on brain activity," he says. "We presented people with a range of smells, some artificial food odours and some real food odours, with both samples including chocolate." Martin used EEG (electroencephalography) technology to record his participants' brain waves as they sniffed the air, and found that in both experiments, the chocolate smell consistently led to a reduction in a particular type of brain activity called theta, which is thought to be an index of attentiveness. "Theta levels dropped significantly across both indexes when testers smelled chocolate."

The experiment also showed there's no need for chocolate snobbery. "I know connoisseurs say posh chocolate, with a higher cocoa content, is better for your health, and it might be in some ways, but when it comes to the smell of chocolate and its resultant relaxing effect, we found it was the same however much milk the bar contains," Martin says. "My guilty secret is Fry's Turkish Delight – it's always in my fridge."

But some of his other scent findings provide more significant practical effects. "Scent can affect employment," he says.

One study found that a combination of perfume and formal dress worn by an applicant led interviewers to rate them as less warm, more manipulative and less appointable. And Martin has shown that people perform less well on cognitive tasks and report more symptoms of ill-health when smelling a "bad" smell.

As a result, Martin says people should be aware of their "olfactory environment" to control their feelings. "People can use scents to improve alertness, wellbeing and anxiety," he says. "For example, another study showed that women in a dentist's waiting room that had been scented with orange reported less anxiety than those in an unscented counterpart."

A separate piece of research saw Martin and his team set up PlayStations loaded with Colin McRae's Rally game, to test the impact of a lemony smell on driving ability. Martin invited men and women to play the game on three different levels and in three different environments, one in a room without any odour, one smelling of lemon, and one of machine oil.

"We found that participants were consistently able to brake more safely and appropriately in the presence of the lemon scent," Martin reports. "It's perhaps because the smell is citrus-y and alerting, and suggests that dangling a lemon-smelling air freshener in the car could make you a better driver."

But as Martin's use of words such as "citrus-y" shows, the psychology of smells is hard to pin down because they are so tough to describe. "The problem is, science doesn't really understand smells. We have vague terms for them, and say things like "it smells like this or that", but we don't have chemical terms for most odours. I think all the answers to the effects of smell will come down to chemistry one day, but we haven't yet got to that level. Scent is described as the Cinderella of the senses because a considerable amount of nonsense is written and talked about it. Our research tries to test the effects of scent on behaviour in a scientifically sound, methodical way."

One thing is for sure, however: the effects of smell tend to be short-lived. "We get used to odours very quickly," Martin explains. "Imagine waking into a strange environment – it will smell strange, but after a while the odour disappears because we become habituated to it. For our experiments, that means odour needs to be delivered in short bursts."

For Easter egg munchers, that means that you'll have to be quick when smelling chocolate as you unwrap it from its foil this weekend. "It's definitely worth having a sniff of Easter egg for a minute or two for chocolate's mood-enhancing qualities," Martin says. "But don't hang around too long, or the stress of not being able to eat it immediately might wipe out the effects completely."